Many articles and packages include or can include a strip of material that has a line of weakness having one or more perforations to aid in tearing the article or package. For example, articles can include wax paper, aluminum foil, disposable bags, and sanitary tissue products, such as toilet tissue, facial tissue, and paper towels manufactured in the form of a web. Sanitary tissue products include lines of weakness to permit tearing off discrete sheets, for example, as is well known in the art. Such products are commonly used in households, businesses, restaurants, shops, and the like.
Typically, a line of weakness consists of a straight perforation across the width of the web. Creating perforations at high speeds and long widths is very challenging. Small vibrations in the equipment can result in non-perforated areas and/or inconsistent quality in the perforation and/or additional wear on the equipment. Further, tight tolerances between equipment must be maintained. Generally, there are three ways to perforate webs: die cutting, laser cutting, and flex blade cutting. Die cutting is a compression or crush cut in which a knife contacts a hardened anvil roll or a male roll interacts with a female roll to create one or more perforations. Die cutting usually is associated with high replacement costs and low speeds. Further die cutting does not allow for accuracy at long widths or mismatched speed operation. Similarly, laser cutting is a high-powered method to perforate webs. Laser cutting is usually used on thicker substrates and on cuts requiring a high degree of accuracy. Still further, flex blade cutting is a cut created by shearing the web. Flex blade cutting requires at least one blade to flex against a relatively stationary blade or anvil during operation to cut the web. Relative to the above cutting methods, flex blade cutting is generally lower cost, can be performed at higher speeds, and can be run at mismatched speeds. In addition to the above, water jet, steam, and spark aperture cutting methods can also be used to create lines of weakness. These methods have been found to be incompatible with the product being manufactured and/or inadequate for high speed, low cost production of perforated webs.
For example, using two rotating rolls to create a shaped line of weakness can be complex and expensive. The two rotating rolls must be matched to come together at exactly the right moment in time. Stated another way, the male roll must be synchronized with the female roll. Further, creating perforations with a rotating male roll and a rotating female roll can require a greater force be imparted to the web to create the line of weakness. Finally, the equipment to create such a line of weakness is large and must operate at lower speeds to maintain proper matching of the rolls.
It has been found that consumers desire products that are usable and have a distinguishing feature over other products. Manufacturers of various products, for example sanitary tissue products, desire that consumers of such products be able to readily distinguish their products from similar products produced by competitors. One way a manufacturer can distinguish its products from other products is to impart physical characteristics into the web that differ from other manufacturers' products. A shaped perforation is one distinguishing characteristic that can be added to the product. The shape of the line of weakness would not only provide a way for consumers to distinguish a manufacture's product, but also communicate to consumers a perception of luxury, elegance, and softness and/or strength.
Further, manufactures desire a shaped perforation that consumers of such products can easily and readily interact with. Often a straight perforation on a sanitary tissue product, for example, can rest directly on the adjacent layer making it difficult to see the end of the sheet. This can make it difficult for a user to locate, grasp, and/or dispense the product. A straight perforation can allow for only a single plane of the product on which a user can grasp for dispensing.
However, producing a web with a shaped perforation adds more complexity to the manufacturing process. As previously stated, tight tolerances and minimal to no vibration are required in manufacturing a line of weakness at the high speeds necessary for commercial viability. Thus, adding a shape to the anvil and/or the blade can increase the risk of introducing processing complexities and complications into commercial manufacturing operations for a perforated web.
Still further, as previously stated, consumers desire a product that they can easily and readily interact with. A shaped perforation adds a degree of complexity to the processing capability of manufactures to provide a product that tears at least as well as a currently marketed product having a straight line of weakness. Further, imparting a shaped line of weakness in the product can lead to unequal perforations and/or inconsistency in tearing.
Accordingly, there is a continuing unmet need for an improved perforating apparatus to manufacture a web with a shaped line of weakness.
Accordingly, there is a continuing unmet need for an improved method to manufacture a web with a shaped line of weakness.
Still further, there is a continuing unmet need for a sanitary tissue product having individual sheets separated by shaped lines of weakness, and which allows consumers to easily and readily interact with the product. More specifically, there is a continuing unmet need for a sanitary tissue product that allows the consumer to grasp the first, exposed sheet of the product readily and easily for dispensing and use.